Orlando Sentinel reporter Vicki McClure analyzed more than 2 million records from three sets of data. The individual-loan information was collected by the Federal Financial Institutions Examination Council under the federal Home Mortgage Disclosure Act, which covers about 80 percent of all home lending nationwide and was reported using U.S. Census tracts. Mortgage-default information was gathered from public records by RealtyTrac Inc., an Irvine, Calif., company that sells foreclosure data online to prospective home buyers. (McClure removed duplicate records from the RealtyTrac data.)

McClure used mapping and statistical-analysis software to determine areas with strong correlations between mortgages defaults and subprime mortgages. After the analysis was complete, the findings were reviewed by Mark E. Johnson, a statistics professor at the University of Central Florida.